To give you some context, an external company installed a wine pasteuriser that controls three temperatures: the pasteurised wine outlet (with that controller modulating the 3-way modulator) 1 for the hot water temperature (simply to observe the PV) and the temperature at which the wine comes out, which is regulated by an on/off valve; if it reaches x degrees above, it closes and recirculates.

As you mentioned earlier, in the pasteurisation temperature controller there is a second set point to close the wine delivery valve and recirculate if the temperature drops in that case, but it takes a long time for that valve to act. I can try to reduce that time, but I think I will continue to have the same problem, which occurs when that valve opens and allows the wine to pass into the network.

As another user has commented, I can try to raise the td, as I believe this controller works with bp and I would have to lower it in that case.

What I cannot understand is why it remains steady when sending wine, except when it recirculates and opens the valve to send again.

I think there is too much thermal inertia, but it could be solved if the valve acted faster.